The service life of a tyre is a cumulative function of storage and service conditions that a tyre is subjected to throughout its life, such as load, speed, inflation pressure, road hazard injury, environmental influences, etc). Since service conditions and tyre maintenance can vary widely, accurately predicting the service life of any specific tyre is not possible.
The influence of higher temperatures on tyre service life may be twofold:
(i) Influence by peak temperatures usually maintained only for short periods of time. Such peak temperatures are typically reached in high speed applications. The tyre’s ability to withstand such heat and/or to dissipate such heat is checked and assessed by the tyre manufacturer and indicated by the tyre’s speed symbol, as written on the tyre’s sidewall as part of its service description.
(ii) The influence of time/temperature exposure. The longer a tyre is exposed to higher temperatures, the more likely it will sustain detrimental changes in materials and properties. Furthermore, the higher the temperatures, the more rapidly these changes will occur. Such changes may reduce the tyre’s robustness/resistance to fatigue, which may result in damage to the tyre.
SEMPERIT recommends the following for tyre storage conditions:
- Avoid storing tyres where they are subject to extreme temperatures.
- Do store tyres at temperatures not exceeding 35°C (95°F), preferable below 25°C (77°F). Tyre operating temperatures may be higher. However, the longer a tyre is exposed to higher temperatures, the shorter its useful service life.
SEMPERIT recommends removing from service all tyres manufactured more than ten years ago. If the tyre has been subjected to any significant time/temperature exposure, SEMPERIT also recommends that the tyre be removed from service earlier. If a customer is unsure as to whether a tyre should be removed from service or not, they should have it inspected by a trained tyre specialist without delay. As established by NHTSA (the National Highway Traffic Administration of the USA) and ASTM (Association for Standardisation of Testing Methods), keeping a tyre at 65°C under certain defined harsh conditions for a duration of five weeks may represent a tyre’s ageing in an extremely hot climate over four to six years.
Another item to be considered is the influence of extremely cold temperatures. Very cold temperatures (below -30°C/-22°F for summer/high-performance tyres and below -50°C/-58°F for winter/all-season tyres) might lead to brittleness. Therefore, tyres in extremely cold temperatures should be carefully warmed up before use.